The long-term objective of the current proposal is to elucidate the role of the gustatory thalamus in taste-guided behavior. The proposed research is intended to investigate the hypothesis that the gustatory thalamus is primarily involved with sophisticated preparatory, but not the consummatory, aspects of taste-guided behavior. The preparatory phase consists of complex perceptual and cognitive strategies that guide the environmental search for potential food sources; the consummatory phase (served by the hindbrain), by comparison, involves eating and drinking responses once food makes contact with the mouth. Three series of experiment will be undertaken using rats with electrophysiologically guided ibotenic acid lesions of the gustatory thalamus. The experiments of Specific Aim number 1 are intended to determine the nature of the lesion-induced higher-order associative learning deficit by examining performance on complex taste information processing tasks which similarly involve the modulation of the strength of an acquired gustatory aversion. By examining performance on instrumental contrast procedures, the research proposed in Specific Aim number 2 will determine if the gustatory thalamus functions as a general reward comparison mechanism such that lesions disrupt all forms of contrast effects involving gustatory rewards. Finally, the experiments of Specific Aim number 3 will determine if the contrast deficits found in rats with lesions of the thalamic taste area result from an underlying dysfunction of gustatory memory. The results of the research proposed in this application will significantly enhance our understanding of the information processing role(s) of the thalamic taste area of the rat.